1. Field of the Invention
The present invention relates to a resin composition, a seamless belt, and an image forming apparatus.
2. Description of the Related Art
Conventionally, image forming apparatuses such as copiers, printers, and facsimile machines configured to form images by electrophotography or electrostatic printing have employed electro-conductive seamless belts for various purposes, including transfer belts such as intermediate transfer belts, conveyor belts, fixing belts, and developing belts.
Main examples of means for adjusting electric resistance of a resin composition include a method of utilizing an electron conductive effect and a method of utilizing an ion conductive effect. As a transfer belt, it is preferable to use a material in an intermediate resistance range (from 106Ω/□ to 1011Ω/□ in terms of surface resistivity). In order to adjust volume resistance of a transfer belt, a resistance controlling agent such as an electro-conductive agent and an ion conductive agent is dispersed in a resin composition.
The method of utilizing an electron conductive effect adds an electro-conductive agent to the resin composition to adjust electric resistance. Generally, this method uses electro-conductive carbon black as the electro-conductive agent. However, in the intermediate resistance range, the amount of change in the surface resistivity rge relative to the amount of change in the additive amount of the electro-conductive carbon black. Therefore, resistance adjustment is difficult with so electro-conductive carbon black.
Further, it is very difficult to disperse an electro-conductive agent in the resin composition uniformly. A transfer belt of which resistance is adjusted according to this method may produce image failures such as white voids and leaks due to unevenness of the electric resistance in the belt.
Furthermore, when the electro-conductive agent is other than carbon black, such as zinc oxide, it is necessary to add the electro-conductive agent in a large amount in order to adjust the surface resistivity in the intermediate resistance range. Addition thereof in a large amount makes the resin composition largely voltage-dependent and brittle to greatly degrade the shapability of the resin composition.
On the other hand, the method of utilizing an ion conductive effect adds an ion conductive agent such as surfactant to the resin composition. This method has a problem that the concentration of the ion conductive agent lowers along with continued electricity application, to thereby change the surface resistivity. Another problem is that the surface resistivity greatly changes according to the temperature and humidity conditions.
There is proposed an electrophotography endless belt that includes a layer made of a resin composition containing: at least one kind of resin selected from the group consisting of polyetheresteramide, polyolefinether, and polyetheramide: polyvinylidene fluoride; and carbon (see Japanese Patent Application Laid-Open (JP-A) No. 2006-313308).
However, the surface resistivity of this proposed belt cannot be lowered unless polyether resin is added in a large amount. As a result of adding polyether resin in a large amount, there occurs a problem that mechanical strength and flame retardancy degrade.